1. Field of the Invention
The present invention relates to a ground contacting system for use in shoes which provide a damping action to cushion foot impact, a 3D force reduction action to reduce force transference and a deflecting action to allow a slight, but detectable displacement of user's foot relative to the ground contacting system.
More particularly, the present invention relates to a ground contacting system including a first plurality of 3D deformable, deflectable, damping elements projecting downward from an undersurface of an outsole and/or a second plurality of 3D deformable, deflectable, damping elements having a portion projecting downward from the outsole undersurface and having a second portion wrapping up above the undersurface of the outsole onto an upper where the elements cushion foot impact, reduce force transference three dimensionally and allow for a slight, but measurable displacement of the user's foot relative to a ground contacting surface of the elements in the direction of the forces associated with foot fall.
2. Description of Related Art
Footwear intended for physical activity includes an upper and a securely attached sole. The upper wraps around some or all of a wearer's foot, and is typically held in place by shoelaces. Soles typically include an inner sole, a midsole, and an outsole. Midsoles are generally formed of a cushioning material while outsoles are wear-resistant layers. Overall, soles are designed to provide stability and absorb impact loading caused by the foot of a wearer coming down upon the ground.
Significant engineering goes into providing and balancing design parameters for stability and cushioning. Special EVA foam materials have been formulated for use in midsoles. Various manufacturers have incorporated devices in the midsole to provide stability, cushioning, or, hopefully, both. For example, one major footwear manufacturer incorporates an air bag that is filled with a high molecular weight gas in order to provide substantial cushioning underneath the heal of the wearer. That manufacturer also provides midsole structure to enhance sole stability that is lost due to the presence of the air bag. Another manufacturer has used a gel-filled bag in the midsole to absorb impact. Another manufacturer provides "cantilever" technology to provide cushioning with a goal toward a minimum loss of stability.
Examples of devices designed to provide stability include heel counters, variable density EVA foams in the midsole, and inelastic straps going from the fore foot to the heel section of the shoe.
It is common knowledge in the footwear industry that a runner will experience less leg fatigue and muscle and joint stress by running on a dirt road than on a paved road over equal distances. Folklore has always attributed the difference to the theory that the dirt road provides a softer or more cushioned surface upon which to run. However, empirical tests have suggested that many dirt roads are just as hard as paved roads when measured under vertical impact loading. The applicants of the present invention have therefore theorized that dirt roads may provide the advantage of a small amount of sliding each time a runner's foot contacts the ground.
When running on a dirt road, the runner's foot will go through a forward motion until it makes initial contact with the ground whereupon it slides forward slightly until coming to a rest. This action is repeated for each step. Because impact is measured as force divided by the amount of time the force is applied, the impact on a leg is lessened by the foot's sliding because the force of each step is applied over a greater amount of time. This is contrasted with running on pavement wherein the foot moves forward between steps and upon initial ground contact the foot comes to an immediate halt without any substantial forward sliding. Thus, the impact load on the foot, and hence the leg, is substantially greater.
Additionally, runners run with their knees bent. Thus, the lower leg forms a pivot point at the knee. During the time that the foot transitions from forward motion to a dead stop there is a rearward force (friction) on the bottom of the shoe by the ground which acts to pivot the lower leg about the knee, thus creating a moment at the knee joint. This moment must be resisted, in part, by the quadriceps and knee ligaments. It is the applicant's theory that when a runner runs on a dirt or gravel road the small amount of forward sliding that occurs upon each footfall reduces the moment at the knee due to impact loads because the amount of time that the load is applied is increased while the magnitude of the load does not change.
Similar kinematics apply to sports other than running. When tennis is played on a clay court the players experience some sliding each time a foot plant is performed. Conversely, when tennis is played on an asphalt court players may experience greater muscle fatigue because the foot cannot slide during sudden stops thus creating greater impact.
Numerous foreign patent and applications and numerous United States patents have disclosed, taught and claimed various techniques for imparting cushioning and stability to a shoe. However, none of these techniques have simultaneously optimized the bio-mechanical characteristics of the shoe. Thus, it would represent an advancement in the art to produce soles that can be continuously woven into the upper so that there is a smooth transition from the sole element to the upper element so that the foot can be better supported and better accommodated by a shoe so constructed.